Some methanogenic Archaea are capable of fixing nitrogen.

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Some methanogenic Archaea, such as Methanosarcina acetivorans, have been shown to have the ability to fix nitrogen under certain conditions. This is due to the presence of nitrogenase, an enzyme responsible for converting atmospheric nitrogen into a form that can be used by the organism for growth and metabolism. However, this process is energetically costly for the methanogens, and they typically rely on other sources of nitrogen for their needs.

Some Methanogenic Archaea Are Capable of Fixing Nitrogen